Method and apparatus for performing quantum secure direct communication by using high-dimensional quantum state based on polarization and phase information in communication system

Abstract

In order to perform quantum secure direct communication using a high-dimensional quantum state quantum state based on polarization and phase information, a method performed by a first device in a communication system may comprise establishing a classic channel with a second device using a random access (RA) preamble and an RA response (RAR) message, receiving a forward pulse including photons in an initial quantum state from the second device, and transmitting a backward pulse representing a plurality of bits per photon by performing phase modulation and polarization modulation on the photons based on assistance of the classic channel

1 . A method performed by a first device in a communication system, the method comprising:
 transmitting, to a second device, a random access (RA) preamble;   receiving, from the second device, an RA response (RAR) message;   establishing a channel with second device, the channel comprising a classic channel;   receiving a forward pulse including photons in an initial quantum state from the second device; and   transmitting a backward pulse representing a plurality of bits per photon by performing phase modulation and polarization modulation on the photons based on assistance of the classic channel.   
     
     
         2 . The method of  claim 1 , further comprising:
 receiving, through the classic channel, information related to a basis used to generate the photons included in the forward pulse; and   generating the backward pulse including classic information based on the information related to the basis.   
     
     
         3 . The method of  claim 1 , further comprising:
 adjusting the photons included in the forward pulse to a common polarization state;   performing phase modulation on photons having the common polarization state;   reconstructing the polarization state of phase-modulated photons to the polarization state of the initial quantum state; and   performing polarization modulation on the photons having the reconstructed polarization state.   
     
     
         4 . The method of  claim 1 , further comprising:
 performing measurement on the initial quantum state; and   transmitting information related to a result of measurement to the second device through the classic channel.   
     
     
         5 . The method of  claim 4 , wherein the forward pulse includes a pair of photons that are branched from a same photon in the second device and then transmitted with a time difference, and
 wherein the photons used for the measurement are selected in units of pair of photons.   
     
     
         6 . The method of  claim 4 , wherein the performing the measurement on the initial quantum state comprises,
 measuring the polarization state of the initial quantum state based on a time difference generated by two paths with different lengths branched according to the polarization state; and   measuring a phase state of the initial quantum state based on interference between two signals included in a pair of photons.   
     
     
         7 . The method of  claim 1 , wherein the backward pulse comprises dummy bits for estimating an error rate for a quantum channel in the second device. 
     
     
         8 . The method of  claim 7 , further comprising:
 transmitting information related to the dummy bits to the second device through the classic channel.   
     
     
         9 . A method performed by a second device in a communication system, the method comprising:
 receiving, to a first device, a random access (RA) preamble;   transmitting, to the second device, an RA response (RAR) message;   establishing a channel with the first device, the channel comprising a classic channel;   transmitting a forward pulse including photons in an initial quantum state from the first device; and   receiving a backward pulse representing a plurality of bits per photon by performing phase modulation and polarization modulation on the photons based on assistance of the classic channel.   
     
     
         10 . The method of  claim 9 , comprising:
 receiving information related to a result of measurement of the initial quantum state of the photons included in the forward pulse; and   suspending quantum communication based on an error rate of a quantum channel determined based on the result of measurement being less than or equal to a threshold.   
     
     
         11 . The method of  claim 9 , further comprising obtaining classic information included in the backward pulse based on the quantum state of the photons included in the backward pulse. 
     
     
         12 . The method of  claim 11 , wherein the quantum state of the photons included in the backward pulse is measured based on a basis used to generate the initial quantum state of the photons included in the forward pulse. 
     
     
         13 . The method of  claim 11 , wherein the obtaining the classic information comprises,
 estimating an error rate of a quantum channel using dummy bits included in the backward pulse; and   decoding a message included in the backward pulse based on at least one decoding parameter determined based on the error rate.   
     
     
         14 . A first device in a communication system, the first device comprising:
 a transceiver; and   a processor connected to the transceiver,   wherein the processor is configured to;   transmit, to a second device, a random access (RA) preamble;   receive, from the second device, an RA response (RAR) message;   establish a channel with the second device, the channel comprising a classic channel;   receive a forward pulse including photons in an initial quantum state from the second device; and   transmit a backward pulse representing a plurality of bits per photon by performing phase modulation and polarization modulation on the photons based on assistance of the classic channel.   
     
     
         15 - 17 . (canceled) 
     
     
         18 . The first device of  claim 14 , wherein the processor is further configured to:
 receive, through the classic channel, information related to a basis used to generate the photons included in the forward pulse; and   generate the backward pulse including classic information based on the information related to the basis.   
     
     
         19 . The first device of  claim 14 , wherein the processor is further configured to:
 adjust the photons included in the forward pulse to a common polarization state;   perform phase modulation on photons having the common polarization state;   reconstruct the polarization state of phase-modulated photons to the polarization state of the initial quantum state; and   perform polarization modulation on the photons having the reconstructed polarization state.   
     
     
         20 . The first device of  claim 14 , wherein the processor is further configured to:
 performing measurement on the initial quantum state; and   transmitting information related to a result of measurement to the second device through the classic channel.   
     
     
         21 . The first device of  claim 20 , wherein the performing the measurement on the initial quantum state comprises,
 measuring the polarization state of the initial quantum state based on a time difference generated by two paths with different lengths branched according to the polarization state; and   measuring a phase state of the initial quantum state based on interference between two signals included in a pair of photons.   
     
     
         22 . The first device of  claim 14 , wherein the backward pulse comprises dummy bits for estimating an error rate for a quantum channel in the second device. 
     
     
         23 . The first device of  claim 22 , wherein the processor is further configured to:
 transmit information related to the dummy bits to the second device through the classic channel.